This invention relates to a method of and apparatus for determining the location of graduated marks in measuring applications, and particularly to apparatus including at least one source of electromagnetic radiation and a plurality of electromagnetic radiation sensors.
Generally, this apparatus has a graduated mark or marks which move between the source and the sensors, the mark being opaque to the radiation and thus causing a radiation shadow to fall on the sensors. The sensors can be used to sense the position of the shadow and thus the mark. The mark movement is, of course, directly related to the measurement being taken.
The mark may alternatively be a gap in an otherwise opaque measuring scale, thus causing a slot of radiation to pass through the gap onto the sensors. The essential requirement is that the mark should cause a detectable restriction in the radiation passing beyond it.
One such measuring apparatus is more fully described in and forms the subject matter of, our co-pending South African patent application No. 79/1964 of even date entitled "Measuring Method and Apparatus".